Safeguarding Your Domain: DNS Security Best Practices and Attack Prevention

by Nikita Serrao

What is DNS security, and why is it important? 

DNS (Domain Name System) security refers to the measures taken to protect the Domain Name System, which translates domain names into IP addresses. It mitigates risks including sensitive data theft, malware, phishing, ransomware attacks, and unauthorised web and non-web callbacks from compromised systems. It's crucial because DNS is a fundamental component of the internet infrastructure, facilitating communication between devices by resolving human-readable domain names to machine-readable IP addresses. 

DNS servers are often targeted in Distributed Denial of Service (DDoS) attacks where the criminals overwhelm the servers with traffic and disrupt services. According to The State of the UAE Cybersecurity Report published in 2024, the UAE suffered 58,538 DDoS attacks in 2023 compared with 7.9million attacks globally. The duration of the outages was less than the global average which the report suggests reveals “a nuanced threat landscape where the intensity of attacks may not always align with global trends.” The report highlighted that the most common industries targeted in DDoS attacks are Banking, Utilities and Government organisations. 

Common Types of DNS Attacks   

DNS attacks can lead to various forms of cybercrime. Here’s a more detailed look at some common types of DNS attacks:

1. DNS Spoofing Attack

Definition: Also known as DNS cache poisoning, is an attack where attackers inject false information into a DNS server's cache, causing the server to return incorrect IP addresses. This redirection leads users to malicious websites instead of their intended destinations.

Impact: The redirection is designed to install malware and leads users to phishing sites where attackers can steal sensitive information such as login credentials and financial details.

2. DNS Hijacking Attack

Definition: In a DNS hijacking attack, attackers modify the DNS settings on a user’s device or network router to redirect traffic to malicious websites without the user's knowledge. 

Impact: This can lead to loss of sensitive data, exposure to malware, and disruption of services.

3. DNS Reflection Attack

Definition: A type of Distributed Denial of Service (DDoS) attack where an attacker sends a high volume of DNS queries with a spoofed source IP address (the victim's address) to DNS servers, causing the servers to flood the victim with DNS responses. 

Impact: Overwhelms the victim's network or servers with traffic, causing downtime and service outages and denial of legitimate access.

4. DNS Flood Attack

Definition: Another form of DDoS attack targeting DNS servers, where attackers flood the server with a large volume of malicious DNS queries, overwhelming its capacity to respond to legitimate DNS requests. 

Impact: Can lead to slow downs or complete unavailability of DNS resolution services, disrupting access to websites and services.

5. Domain Reputation Attack

Definition: Attackers exploit DNS vulnerabilities to associate a domain with malicious activities, harming its reputation. This can involve sending spam emails from the domain or using it for phishing. 

Impact: The affected domain may be blacklisted, leading to a loss of trust and business opportunities.

6. DNS Tunnelling 

Definition: DNS tunnelling involves encoding data within DNS queries and responses to bypass network security controls. This technique can be used for data exfiltration or command and control communications by malware. 

Impact: Allows attackers to covertly transfer data out of a network, bypassing firewalls and other security measures. 

7. DNS Cache Poisoning

Definition: It involves corrupting the DNS cache by injecting false data. This results in the resolver providing incorrect IP addresses for domain queries. Cache poisoning can be achieved through various means, including DNS spoofing attacks.

Impact: Redirects users to malicious websites.

8. DNS Amplification

Definition: It involves exploiting misconfigured DNS servers to generate a large volume of traffic directed towards a target system, often in a Distributed Denial of Service (DDoS) attack.

Impact: Overwhelms the target system with a flood of DNS responses, potentially causing service disruption, downtime, or even cause ing the server to crash in severe cases.

Understanding DNS Security Protocols 

To protect your applications and services, it’s crucial that DNS security protocols are deployed. Here's an overview of some of the key DNS security protocols that will help protect your organisation:

1. DNSSEC (Domain Name System Security Extensions)

DNSSEC is a suite of extensions to DNS that adds a layer of security by enabling DNS responses to be authenticated. Orixcom Managed Cisco Umbrella also offers DNSSEC support by conducting validation on queries transmitted from Umbrella resolvers to upstream authorities. 

How It Works: 

1. Digital Signatures: DNSSEC uses public-key cryptography to sign DNS data. Each DNS zone has a pair of cryptographic keys: a private key to sign the data and a public key to verify the signatures. 
2. Chain of Trust: The signatures create a chain of trust from the DNS root zone down to individual domain names. When a DNS resolver receives a DNSSEC-signed response, it can verify the data's authenticity and integrity by checking the digital signatures against the public keys. 
3. Authenticated Responses: If the data has been tampered with or is not signed correctly, the resolver will detect the discrepancy and reject the response. 

Benefits: 

1. This feature assures customers that Cisco Umbrella safeguards their organisation against cache poisoning attacks, eliminating the need for local validation.
2. Ensures the integrity and authenticity of DNS data. 

2. DNSCrypt

DNSCrypt is a protocol that authenticates and encrypts DNS traffic between the user's device and the DNS resolver. It is utilised by Umbrella to authenticate communications between Cisco devices and Umbrella's Integration feature.

How It Works: 

1. Encryption: DNSCrypt encrypts DNS queries and responses, preventing eavesdropping and manipulation by intermediaries. 
2. Authentication: It uses cryptographic signatures to verify that the responses come from the specified DNS resolver and have not been tampered with. 
3. In the case of Cisco Umbrella, when configured with the "parameter-map type umbrella" command and enabled on a WAN interface using "umbrella out," DNSCrypt is activated, triggering the download, validation, and parsing of a certificate. This process negotiates a shared secret key for encrypting DNS queries, with a new key renegotiated hourly for enhanced security.

Benefits: 

1. Enhanced Security: DNSCrypt encrypts DNS traffic, safeguarding against unauthorised access and DNS manipulation, ensuring data privacy and integrity.
2. Automatic Key Rotation: The hourly renegotiation of shared secret keys enhances security by mitigating the risk of key compromise, ensuring continuous protection against potential threats like DNS spoofing.

3. DNS-over-HTTPS (DoH)

DoH is a protocol that performs DNS resolution over HTTPS, encrypting the DNS queries and responses within standard HTTPS traffic. Cisco Umbrella enhances support for DNS encryption with DNS over HTTPS (DoH), fortifying internet security by encrypting DNS queries, thereby mitigating risks posed by potential threats. This integration bolsters network defences, ensuring a safer and more resilient browsing experience for users.

How It Works: 

1. Integration with HTTPS: DNS queries are sent via HTTPS, making them indistinguishable from regular web traffic. 
2. Encryption: This encryption prevents third parties from seeing the DNS queries and responses, protecting user privacy and security. 

Benefits: 

1. Obscures DNS traffic within regular HTTPS traffic, making it harder for attackers and ISPs to monitor or manipulate. 
2. Enhances privacy and security by using strong HTTPS encryption. 

4. DNS-over-TLS (DoT) 

DoT is a protocol that uses TLS (Transport Layer Security) to encrypt DNS queries and responses between the user's device and the DNS resolver. 

How It Works: 

1. Encryption: DNS queries are sent over a secure TLS connection, preventing eavesdropping and tampering. 
2. Standard Port: Typically uses port 853, distinct from regular DNS traffic which uses port 53. 

1. Provides strong encryption, protecting DNS traffic from interception and manipulation. 
2. Helps prevent DNS-based attacks by ensuring the confidentiality and integrity of DNS queries and responses. 

Summary of Benefits of DNS Security Protocols 

1. Enhanced Privacy: By encrypting DNS queries, these protocols protect user data from being intercepted and analysed. 
2. Integrity and Authenticity: Protocols like DNSSEC ensure that DNS responses are authentic and have not been tampered with, preventing various forms of DNS attacks. 
3. Protection Against Attacks: These protocols help mitigate risks such as DNS spoofing, cache poisoning, and man-in-the-middle attacks, thereby enhancing overall internet security. 

DNS Security Best Practices  

Ensuring the security of DNS infrastructure is critical for protecting against various cyber threats. Here are some best practices for DNS security, including the use of Orixcom Managed Cisco Umbrella, a cloud-delivered security service that provides comprehensive DNS-layer protection. 

1. Implement Strong Passwords and Access Controls 

1. Secure your DNS management interfaces and systems by implementing robust authentication mechanisms and access controls.
2. One way of enhancing security measures is by using Multi-Factor Authentication (MFA) such as Duo MFA to add an additional layer of defence. This ensures that even if a password is compromised, unauthorised access is effectively prevented.

2. Regularly Update DNS Software and Patches 

1. Keep DNS software up to date with the latest patches and updates to protect against vulnerabilities.
2. Establish a regular update schedule and promptly apply patches released by software vendors. 

3. Enable DNSSEC for Domain 

1. Implement DNSSEC (Domain Name System Security Extensions) to add a layer of authentication to DNS responses.
2. DNSSEC ensures the integrity and authenticity of DNS data, protecting against spoofing and cache poisoning attacks. 

4. Monitor DNS Traffic for Anomalies 

1. Continuously monitor DNS traffic for unusual patterns that may indicate an attack.
2. Use network monitoring tools and services like Cisco Umbrella to detect and respond to suspicious DNS activity. 

5. Utilise DNS Firewall 

1. Deploy a DNS firewall to filter out malicious DNS queries and block access to known malicious domains.
2. Cisco Umbrella provides DNS-layer security that proactively blocks requests to malicious domains, helping to prevent malware infections and data exfiltration.

6. Limit Zone Transfer 

1. Restrict zone transfers to authorised secondary DNS servers to prevent unauthorised access to DNS zone data.
2. Configure access controls and use TSIG (Transaction Signature) keys to authenticate zone transfer requests. 

7. Implement Rate Limiting 

1. Apply rate limiting to DNS queries to mitigate the impact of DDoS attacks.
2. Rate limiting helps protect DNS servers from being overwhelmed by high volumes of requests, ensuring service availability. 

8. Use Anycast DNS 

1. Deploy Anycast DNS to distribute DNS queries across multiple geographically dispersed servers.
2. Anycast improves DNS redundancy, reduces latency, and enhances resilience against DDoS attacks by spreading the load across multiple servers. 

9. Integrating Cisco Umbrella for Enhanced DNS-layer Security 

Cisco Umbrella is a cloud-delivered security service that uses DNS to block threats across all ports and protocols. It stops malware early and prevents infected machines from communicating with attackers.

Key Features: 

1. Threat Intelligence: Uses Cisco's threat intelligence to identify and block malicious domains and IPs. 
2. Content Filtering: Enforces acceptable use policies by blocking access to inappropriate or harmful content. 
3. Visibility: Umbrella offers detailed reporting and visibility into DNS requests and traffic patterns, providing insights into cloud applications used within your organisation. This enables you to identify potential risks and easily block specific applications.
4. Integration: Easily integrates with existing security infrastructure and provides seamless protection for both on-premises and remote users.
   
5. Web Security: Directs risky domain requests to a selective proxy for in-depth URL and file inspection, effectively protecting critical infrastructure without causing delays or impacting performance.

Mitigation Strategies for DNS Attacks 

Mitigating DNS attacks requires a combination of proactive and reactive strategies to ensure the resilience and integrity of DNS infrastructure. Here are some key mitigation strategies: 

A. DDoS Mitigation Techniques 

• Implement rate limiting to control the number of requests a DNS server can process from a single source within a specified timeframe. 
• This will help prevent the server from being overwhelmed by excessive requests, mitigating the impact of DDoS attacks. 

• Distributes DNS queries across multiple geographically dispersed servers.
• Enhances load balancing, reduces latency, and improves redundancy.
• Cisco Umbrella leverages Anycast DNS routing for robust, secure, and reliable DNS services, ensuring optimal performance and increasing protection against cyber threats.

• Route traffic through traffic scrubbing centers where malicious traffic is filtered out before reaching the DNS server. 
• Cisco Umbrella offers DDoS mitigation solutions that include traffic scrubbing. 

• Continuously monitor DNS traffic for unusual patterns that may indicate a DDoS attack. 
• Use network monitoring tools to detect and respond to potential DDoS activity in real-time. 

B. Response Plans for DNS Attacks 

• Detection: Mechanisms to detect DNS attacks quickly.
• Containment: Strategies to isolate affected systems and prevent the spread of the attack.
• Remediation: Measures to address the attack and return to normal operations.
• Recovery: Procedures to recover from the attack, including restoring backups and verifying system integrity.

• Conduct regular drills and simulations of DNS attack scenarios to ensure the response team is prepared. 
• Helps identify weaknesses in the response plan and improves the team’s readiness to handle real attacks. 

• Internal Communication: Ensure all relevant teams are informed and coordinated.
• External Communication: Provide timely updates to customers and partners to maintain trust and transparency.

C. Collaborate with ISPs and CDNs

1. Engage with Internet Service Providers (ISPs)

• Collaborate with ISPs to implement network-level protections against DNS attacks.
• ISPs can provide upstream filtering and other mitigation techniques to reduce the impact of attacks before they reach your infrastructure.

2. Utilise Content Delivery Networks (CDNs)

• Leverage CDNs to offload DNS traffic and provide additional layers of protection. 
• CDNs distribute traffic across multiple nodes, improving redundancy and resilience against DDoS attacks. 

By implementing these mitigation strategies, organisations can significantly enhance their defences against DNS attacks. Proactive measures like rate limiting, Anycast DNS, and collaboration with ISPs and CDNs, combined with a well-defined response plan, will help ensure the resilience and integrity of DNS infrastructure. Additionally, leveraging services like Cisco Umbrella can provide comprehensive protection and monitoring to further mitigate the risk of DNS attacks.

FAQs 

1. Which is the most common type of attacks against DNS? 
   The most common type of attack against DNS is the Distributed Denial of Service (DDoS) attack. In a DNS DDoS attack, attackers overwhelm DNS servers with a massive volume of requests, rendering them unable to respond to legitimate queries. This type of attack can disrupt the resolution of domain names, making websites and online services inaccessible to users. DNS DDoS attacks exploit the critical role of DNS in internet connectivity, aiming to cause widespread service outages and operational disruptions. Mitigating these attacks typically involves strategies like rate limiting, Anycast DNS, and traffic scrubbing, as well as collaboration with ISPs and content delivery networks to filter and disperse malicious traffic. 
   
   
2. How can I prevent DNS hijacking attacks?  
   To prevent DNS hijacking attacks, implement a combination of security measures including strong access controls, the use of multi-factor authentication (MFA) for administrative access, and regularly updating and patching DNS servers to fix vulnerabilities. Additionally, employ DNSSEC (Domain Name System Security Extensions) to authenticate DNS responses and ensure data integrity, and monitor DNS traffic for anomalies that could indicate unauthorised changes. Using reputable DNS providers with robust security measures and enabling features like DNS over HTTPS (DoH) or DNS over TLS (DoT) to encrypt DNS queries can also help protect against hijacking attempts. 
   
   
3. What is a DNS security solution? 
   A DNS security solution is a comprehensive approach that incorporates various technologies and practices to protect the Domain Name System (DNS) from cyber threats like spoofing, cache poisoning, and DDoS attacks. It includes implementing DNSSEC for data integrity and authentication, using encryption protocols such as DNS over HTTPS (DoH) and DNS over TLS (DoT) to secure DNS queries, deploying DNS firewalls to filter malicious traffic, and leveraging threat intelligence services like Cisco Umbrella to provide advanced protection and monitoring. These measures collectively enhance the security, reliability, and resilience of DNS infrastructure.